Ethiopia's national electoral board is investigating widespread allegations of fraud in Sunday's general elections.
This ballot paper was allegedly pre-marked in favour of the ruling party
Both the main opposition coalition and the ruling party have lodged complaints - together covering more than one third of the 547 constituencies.
The first official results show opposition landslides in the capital.
Both sides have claimed victory but the ruling EPRDF party has accepted that the opposition has made huge gains - winning at least a third of all seats.
In the last parliament, the opposition only held 12 seats and the Ethiopian People's Revolutionary Democratic Front (EPRDF) has governed the country since 1991.
These are Ethiopia's third multi-party election and there was massive interest, with campaigning far more open than in previous polls.
Nine official results have been declared, even though the electoral board had said the first results would be released on Saturday.
The results confirmed unofficial reports of a landslide for the Coalition for Unity and Democracy (CUD) in the capital, Addis Ababa.
Its candidates won between 75% and 85% of the votes cast and several ministers lost their seats.
Voter turnout was higher than in previous polls
The BBC's Mohammed Adow in Addis Ababa said the size of the opposition victory in the city has surprised many people, even if they were expected to do well.
Our correspondent says residents of the capital are the most politically active in the country, while the city is home to many unemployed people.
In rural areas, however, the government is everything - landlord and provider of fertiliser, loans for farm tools and food aid during times of drought.
The CUD has lodged complaints about voting in the entire Amhara region, where there are 138 constituencies.
The Oromo People's Democratic Organisation, a member of the ruling EPRDF, meanwhile wants re-runs in 60 of the 178 seats in the Oromia region.
The opposition Oromo Federal Democratic Movement wants re-runs across the region.
There have also been complaints of fraud in the Southern Nations, Nationalities and Peoples region.
New elections will be held on Sunday in six polling stations in Oromia and SNNP after cases of ballot-box stuffing and fraud, the Electoral Board says.
The European Union noted scattered irregularities on Sunday, such as pre-marked ballot papers, intimidation and children voting.
Electoral Board spokesman Getahun Amogne told the BBC that it would be able to investigate all the complaints in time to release final results by 8 June.
However, he said that provisional results would not be published on Saturday, as previously indicated.
Information Minister Simon Bereket says the ruling EPRDF has won more than 300 seats, but the opposition reject this.
He told the BBC that judging from poll returns the opposition had won about a third of the seats.
But the CUD has also claimed that it will have enough seats to form a government.
The CUD draws much of its support from the Amhara community which has traditionally ruled Ethiopia.
It is demanding changes to the constitution and a tougher line with Eritrea - the country's neighbour, with which Ethiopia fought a bitter war over their disputed border.
Following opposition allegations of fraud, Prime Minister Meles Zenawi ordered a month-long ban on demonstrations.
Mr Zenawi also took control of the security forces in the capital Addis Ababa, in moves he said were meant to ensure post-election stability.